From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt --- drivers/leds/trigger/ledtrig-cpu.c | 176 +++++++++++++++++++++++++++++++++++++ 1 file changed, 176 insertions(+) create mode 100644 drivers/leds/trigger/ledtrig-cpu.c (limited to 'drivers/leds/trigger/ledtrig-cpu.c') diff --git a/drivers/leds/trigger/ledtrig-cpu.c b/drivers/leds/trigger/ledtrig-cpu.c new file mode 100644 index 000000000..679323c2c --- /dev/null +++ b/drivers/leds/trigger/ledtrig-cpu.c @@ -0,0 +1,176 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * ledtrig-cpu.c - LED trigger based on CPU activity + * + * This LED trigger will be registered for first 8 CPUs and named + * as cpu0..cpu7. There's additional trigger called cpu that + * is on when any CPU is active. + * + * If you want support for arbitrary number of CPUs, make it one trigger, + * with additional sysfs file selecting which CPU to watch. + * + * It can be bound to any LED just like other triggers using either a + * board file or via sysfs interface. + * + * An API named ledtrig_cpu is exported for any user, who want to add CPU + * activity indication in their code. + * + * Copyright 2011 Linus Walleij + * Copyright 2011 - 2012 Bryan Wu + */ + +#include +#include +#include +#include +#include +#include +#include +#include "../leds.h" + +#define MAX_NAME_LEN 8 + +struct led_trigger_cpu { + bool is_active; + char name[MAX_NAME_LEN]; + struct led_trigger *_trig; +}; + +static DEFINE_PER_CPU(struct led_trigger_cpu, cpu_trig); + +static struct led_trigger *trig_cpu_all; +static atomic_t num_active_cpus = ATOMIC_INIT(0); + +/** + * ledtrig_cpu - emit a CPU event as a trigger + * @ledevt: CPU event to be emitted + * + * Emit a CPU event on a CPU core, which will trigger a + * bound LED to turn on or turn off. + */ +void ledtrig_cpu(enum cpu_led_event ledevt) +{ + struct led_trigger_cpu *trig = this_cpu_ptr(&cpu_trig); + bool is_active = trig->is_active; + + /* Locate the correct CPU LED */ + switch (ledevt) { + case CPU_LED_IDLE_END: + case CPU_LED_START: + /* Will turn the LED on, max brightness */ + is_active = true; + break; + + case CPU_LED_IDLE_START: + case CPU_LED_STOP: + case CPU_LED_HALTED: + /* Will turn the LED off */ + is_active = false; + break; + + default: + /* Will leave the LED as it is */ + break; + } + + if (is_active != trig->is_active) { + unsigned int active_cpus; + unsigned int total_cpus; + + /* Update trigger state */ + trig->is_active = is_active; + atomic_add(is_active ? 1 : -1, &num_active_cpus); + active_cpus = atomic_read(&num_active_cpus); + total_cpus = num_present_cpus(); + + led_trigger_event(trig->_trig, + is_active ? LED_FULL : LED_OFF); + + + led_trigger_event(trig_cpu_all, + DIV_ROUND_UP(LED_FULL * active_cpus, total_cpus)); + + } +} +EXPORT_SYMBOL(ledtrig_cpu); + +static int ledtrig_cpu_syscore_suspend(void *data) +{ + ledtrig_cpu(CPU_LED_STOP); + return 0; +} + +static void ledtrig_cpu_syscore_resume(void *data) +{ + ledtrig_cpu(CPU_LED_START); +} + +static void ledtrig_cpu_syscore_shutdown(void *data) +{ + ledtrig_cpu(CPU_LED_HALTED); +} + +static const struct syscore_ops ledtrig_cpu_syscore_ops = { + .shutdown = ledtrig_cpu_syscore_shutdown, + .suspend = ledtrig_cpu_syscore_suspend, + .resume = ledtrig_cpu_syscore_resume, +}; + +static struct syscore ledtrig_cpu_syscore = { + .ops = &ledtrig_cpu_syscore_ops, +}; + +static int ledtrig_online_cpu(unsigned int cpu) +{ + ledtrig_cpu(CPU_LED_START); + return 0; +} + +static int ledtrig_prepare_down_cpu(unsigned int cpu) +{ + ledtrig_cpu(CPU_LED_STOP); + return 0; +} + +static int __init ledtrig_cpu_init(void) +{ + unsigned int cpu; + int ret; + + /* Supports up to 9999 cpu cores */ + BUILD_BUG_ON(CONFIG_NR_CPUS > 9999); + + /* + * Registering a trigger for all CPUs. + */ + led_trigger_register_simple("cpu", &trig_cpu_all); + + /* + * Registering CPU led trigger for each CPU core here + * ignores CPU hotplug, but after this CPU hotplug works + * fine with this trigger. + */ + for_each_possible_cpu(cpu) { + struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu); + + if (cpu >= 8) + continue; + + snprintf(trig->name, MAX_NAME_LEN, "cpu%u", cpu); + + led_trigger_register_simple(trig->name, &trig->_trig); + } + + register_syscore(&ledtrig_cpu_syscore); + + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "leds/trigger:starting", + ledtrig_online_cpu, ledtrig_prepare_down_cpu); + if (ret < 0) + pr_err("CPU hotplug notifier for ledtrig-cpu could not be registered: %d\n", + ret); + + pr_info("ledtrig-cpu: registered to indicate activity on CPUs\n"); + + return 0; +} +device_initcall(ledtrig_cpu_init); -- cgit v1.3.1